Store any unused modeling chocolate it in an airtight container. Stays good for a long time. My instructor says that modeled stuff can stay good for up to and possibly over a year if store in airtight container. I have some from two weeks ago that is still good for modeling.
The problem with saying one bag of melts is that wilton distributes 12 and 14 oz bags. so if youre going to use 12 oz of melts, you would use 6 oz of glucose, which is corn syrup. If you are going to use 14 oz of melts, you would use 7 oz of glucose.
I used normal corn syrup and the chocolate did not want to hold its shape. So the second time I made it after the class I used wiltons glucose and it worked perfectly. And its a ll pre-measured in the container so i knew I had the right amount.
I use a double boiler to melt the chocolate until smooth. Then I let it sit a minute or two then start folding in the glucose (or corn syrup). Dont mix it, fold it. If it starts to get sort of a shiny oily look then you are over doing it. Let it sit and get a sort of matte finish to it. Once combined, wrap the modeling chocolate up in plastic wrap and let it sit over night.
Then, when ready to use, cut off a portion and start kneading it until it is plyable.
Just remember that if it starts getting oily looking youre over working it. Just set it down and let it rest for like 5 minutes or so. If you over work it the oils will separate from the chocolate and it will be ruined.
When mixing in color, just knead it into the modeling chocolate. It is NOT done during the melting phase.
Cut off some modeling chocolate, it will be kinda hard at first, and knead it until soft. Then take a tooth pick and place some color on the chocolate and knead it in. Add more to get desired color.
I answered all of your questions above too. But, basically mix it then wrap it in plastic wrap and let it sit on the counter over night. I also stick my in a gallon ziploc bag just for extra precautions.
You can use water to attach some modeled parts together. We used water to attach calla lily stamens, minor things can be fused together using water. But for other things, such as attaching star gazer lily petals together we used melted candy melts as a glue.
You can see in my pictures the candy melt we used as glue, we were out of class time so everyone was rushing to assemble the pieces, in reality I would make sure you cant see it. But anyways, for the orchid center we used water to keep that in place.